1. Field of the Invention
The present invention relates to a synthetic film of zeolite crystal body for use in separating a useful component from a mixture and a method for manufacturing the zeolite film. The synthetic film according to the invention provides not only a high separation efficiency due to ceramic pores, but also molecular sieving properties and properties as a catalyst of zeolite.
2. Related Art Statement
Conventional process for separating a useful component from a mixture are known, such as by distillation filtration, and adsorption. In the distillation process, since the mixture should be heated up in order to separate the useful component therefrom, the method has a disadvantage in consuming energy. Further, the method has other disadvantages in that the apparatus for performing the distillation method is relatively large; it is difficult to separate the useful component when its boiling point is close to the other of components, and the distillation cannot be applied to the mixture having a low vapor pressure and low heat resistance properties.
In the filtration process, there are also drawbacks such as the hydrocarbon polymer membrane cannot be put into wide use, a small molecular component cannot be separated from the mixture and the filter per se does not have heat resistance properties and high strength. Further, in the adsorption process, the apparatus is relatively large, and it is difficult to separate a highly concentrated useful component from the mixture, since the useful component is separated from the mixture with the aid of equilibrium in adsorption.
The conventional methods mentioned above are mainly used for separating and refining reactants and products of reactions. Recently, a synthetic inorganic film comprising zeolite crystal held on a ceramic supporting body has been developed. Zeolite, alminosilicate crystal, is widely used as powder in form for molecular-sieve, catalyst, etc. However, with this synthetic film, reaction of the mixture can be performed, and then the products successively separated. Such synthetic film is, for instance, disclosed in Japanese Patent Preliminarily Publication Nos. 61-107902, 1-148771 and 3-112808.
However, in these publications, there is no detailed description concerning an optimum condition of the ceramic supporting body and zeolite held thereon, which constitutes the synthetic film, and the method for manufacturing such synthetic film having the optimum condition. Furthermore, according to the method disclosed in these publications, a highly densified film cannot be obtained. Therefore, the separating and refining cannot be performed successively in reaction of the mixture with such synthetic film, and a synthetic film having high strength cannot be obtained. Further, in the synthetic film, zeolite is held on a honeycomb-like ceramic substrate with pores having a mean diameter of several millimeters or more. The purpose for holding a zeolite on such a substrate is not to utilize the zeolite as a filter but to reduce the pressure loss. Thus it is not possible to separate the useful component from the mixture with the aid of pores having a mean diameter of smaller than ten .ANG., formed in the zeolite crystal.